Method of producing spark plug center electrode

ABSTRACT

A method for the production of a spark plug center electrode comprising the steps of preparing a plate for extrusion from a clad plate produced by bonding a corrosion-resistant metal plate and a good heat conducting metal plate together, and coldextruding the plate for extrusion to a rod form.

United States Patent [1911 Yamaguchi et al.

METHOD OF PRODUCING SPARK PLUG CENTER ELECTRODE Inventors: Terumoto Yamaguchi, Anjo;

Kanemichi lzumi, Oobu, both of Japan Assignee: Nippondenso Co., Ltd., Kariya-shi,

Aichi-ken, Japan Filed: Aug. 1, 1972 Appl. No.: 277,101

Foreign Application Priority Data Apr. 18, 1972 Ja'pan.....' 17-39350 U.s. c1 72/258, 29/25.12 Int. Cl. B2lc 23/22 Field of Search 72/258; 29/25.l2, 25.14, 29/25.]7, 25.18; 313/141 [4 1 Apr. 16, 1974 [56] References Cited UNITED STATES PATENTS 3,144,576 8/1964 Hagmaier 72/253 2,955,222 10/l960 Beesch 313/141 Primary Examiner-Charles W. Lanham, Jr. Assistant Examiner-Robert M. Rogers Attorney, Agent, or Firm-Cushman, Darby &

Cushman [5 7] ABSTRACT -A method for the production of a spark plug center 2 Claims, 5 Drawing Figures METHOD OF PRODUCING SPARK PLUG CENTER ELECTRODE BACKGROUND OF THE INVENTION 2. Description of the Prior Art In a known method of producing a spark plug center electrode, a covering member is produced by boring a rod of corrosion-resistant metal such as nickel and then a rod-shaped core member consisting of a good heat conducting metal such as copper is inserted into and soldered to the covering member. A disadvantage of this prior art method is that since the bore for receiving the core member of good heat conducting metal is formed in the covering member of corrosion-resistant metal by the process of cutting, there is a problem from mass production point of view. Moreover, it is difficult to ensure a positive bonding between .the core member and the covering member-with the resultant instability in the production-process.

SUMMARY OF THE INVENTION To solve the foregoing problems, it is an object of the I present invention to provide a method. for the producrod form by the process of cold-extrusion, whereby the I method is well suited for mass production and the production process is also stabilized.

Since the method according to the present invention comprises a first step of preparing a platefor extrusion from a clad plate composed of a corrosion-resistant metal plate and a good heat conducting metal plate bonded together, and a second step of cold-extruding the plate for extrusion to a rod form, there is no need to count upon the corrosion-resistant metal plate and the good heat conducting meta] platebeing bonded together during the cold exclusion operation, and more-. over there is no possibility that any foreign matters are 1 included between the covering member of corrosionresistant metal and the core member of good heatconducting metal and that air or the like is trapped between the two metals, thereby ensuring a very stable production process. Also since the platefor extrusion is prepared from the clad plate, the plate for extrusion a produced in a simple operation and moreover the core member can be covered with the covering member without requiring any cutting operation, thereby ensuring a higher mass production efficiency.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side view of a clad plate employed in the method of producing a spark plug center electrode ac- '2 FIG. 4 is a fractional longitudinal sectional view of a cold extrusion die in which the plate of FIG. 2 or 3 may be inserted.

FIG. 5 is a longitudinal sectional view of a center electrode extruded by the cold extrusion die shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will now be explained with reference to an embodiment illustrated in the drawings. FIG. 1 illustrates a clad plate 3 formed by bonding a plate 1 of corrosion-resistant metal such as nickel to a plate 2 of good heat conducting metal such as copper. While it is more economical to form the clad plate 3 by the process of cold or'hot pressure welding, the clad plate 3 may also be formed by such means as soldering or explosion pressure welding. In the first step of the method of the embodiment, the clad plate 3 composed of the corrosion-resistant metal plate 1 and the good heat conducting metal plate 2 is cut out by a press or the like into hexagonal columns to produce plates for extrusion 4 as shown in FIG. 2 or alternatively the clad plate 3 is cut into long strips of the material so that each of the long strips is cut out into materials for extrusion 4 of square columnar shape as shown in FIG. 3.

If necessary, the corners of the hexagonal or square columnar plate for extrusion 4 may be removed.

In the second step, the plate for extrusion 4 prepared in the first step is inserted in an extrusiondie 5 of a cold extruding machine and pressure is then applied thereto by means of an extrusion punch 6 so that when a product is formed which comprises a cup-shaped covering member 7 consisting of the corrosion-resistant metal.

as compared with a cylindrical extrusion plate, and

moreover by cutting out the hexagonal or square columnar extrusion plate material 4 from the clad plate 3, the loss in the material can be reduced considerably as compared with the cylindrical extrusion plate material 4. Following the extrusion, if necessary, the extruded product is subjected to a finishing operation such as sizing to produce a finished center electrode of any desired dimension which is then assembled into a spark plug. I

We claim:

l. A method of producing a spark plug center electrode comprising a core member consisting of a good heat conducting metal and a corrosion-resistant metal enclosing the sparking-side end and the side portions of the core member, the method comprising the steps of preparing the extrusion plate material from a clad plate formed by bonding a corrosion-resistant metal plate and a good heat conducting metal plate together, cutting said extrusion plate materialin a square columnar shape out of said clad plate, and cold-extruding said extrusion plate material to a rod form.

2. A method of producing a spark plug center elec trode comprising a core member consisting of a good heat conducting metal and a corrosion-resistant metal enclosing the sparking side end and the side portions of the core member, the method comprising the steps of ting said extrusion plate material in a hexagonal columpreparing an extrusion plate material from a clad plate nar shape out of said clad plate, and cold-extruding said formed by bonding a corrosion-resistant metal plate extrusion plate material to a rod form.

and a good heat conducting metal plate together, cut- 

1. A method of producing a spark plug center electrode comprising a core member consisting of a good heat conducting metal and a corrosion-resistant metal enclosing the sparking-side end and the side portions of the core member, the method comprising the steps of preparing the extrusion plate material from a clad plate formed by bonding a corrosion-resistant metal plate and a good heat conducting metal plate together, cutting said extrusion plate material in a square columnar shape out of said clad plate, and cold-extruding said extrusion plate material to a rod form.
 2. A method of producing a spark plug center electrode comprising a core member consisting of a good heat conducting metal and a corrosion-resistant metal enclosing the sparking side end and the side portions of the core member, the method comprising the steps of preparing an extrusion plate material from a clad plate formed by bonding a corrosion-resistant metal plate and a good heat conducting metal plate together, cutting said extrusion plate material in a hexagonal columnar shape out of said clad plate, and cold-extruding said extrusion plate material to a rod form. 